Apparatus and method for ion mobility spectrometry and sample introduction

ABSTRACT

The IMS apparatus and methods described in this invention involve setting the ion detector at the highest potential of the drift tube and setting the ionization source at ground or near ground potential. The methods allow significantly simple sample introduction without the limitation of the high potential (voltage) concern of the front end sample delivery. The invention also describes bringing samples directly into the ion mobility drift tube. The invention further describes using single syringe for sample introduction via an electrospray ionization method.

The present application claims the benefit of and priority tocorresponding U.S. Provisional Patent Application No. 61/452,117, filedMar. 13, 2011 respectively, the entire content of the application isherein incorporated by reference.

BACKGROUND OF THE INVENTION

The needle in some commercial electrospray ionization (ESI) sources isoperated at kilovolt potentials during electrospray operation. For suchESI sources, a longer dielectric liquid transfer line of several inchesis typically configured between the ground potential injector valve andthe ESI needle to allow a gradual drop in kilovolt potential through thesample solution. A high electric field gradient in the transfer tube isavoided to minimize sample heating, electrophoretic and electrolysiseffects during Flow injection analysis (FIA). Liquid transfer lines canbe reduced in length when an ESI source in configured with a groundedneedle, however, even with grounded ESI needles, the dead volume due tothe transfer lines cannot be entirely eliminated. For ion mobilityspectrometer (IMS) applications where small amounts of sample areavailable for injection, sample dilution or losses due to injectorvalve, connector and transfer line dead volumes and surfaces maycompromise the limit of detection.

SUMMARY OF THE INVENTION

The IMS apparatus and methods described in this invention involvesetting the ion detector at the highest potential of the drift tube andsetting the ionization source at ground or near ground potential. Themethods allow significantly simple sample introduction without thelimitation of the high potential (voltage) concern of the front endsample delivery. The invention also describes bringing samples directlyinto the ion mobility drift tube. The invention further describes usingsingle syringe for sample introduction via an electrospray ionizationmethod.

This invention reduces or eliminates cross contamination, solventconsumption, liquid dead volume, and waste by having the sampling andspray needle the same apparatus. The sampling and spray needleconfigured with an auto injector apparatus, continuous infusion syringepump, or used in manual injection is introduced directly into the IMS.Such a sampling and spray needle eliminates the need for injectorvalves, transfer lines or additional fluid delivery systems into IMSinstruments. The injector needle and an ESI source has been configuredsuch that the sample solution can be sprayed directly from the injectorneedle tip. The injector needle does not need to be introduced into theESI source region through a guide. The needle can be configured as areusable or disposable tip. The liquid spray flow rate is set by theauto or manual injector sample injection flow rate. This flow rate canbe set to optimize IMS analysis and sample throughput. In addition,automation of the direct spray needle can be achieved by setting uparray of the spray needles that are loaded in a manner that rotatesand/or moves to the next spray needle in the ESI source region.

The invention comprises a reusable or disposable needle configured in anauto-injector or a manual injector which serves as the means to remove asample solution from a container and transport such solution to anatmospheric pressure ionization (API) source (such as ESI or APCI)wherein the needle is to deliver sample directly into the API sourceand/or desolvation region. Such fixed or disposable needle, whenintroduced into an API source, becomes the liquid introduction channelor tube in the nebulizer probe of an APCI source, the nebulizerapparatus of a pneumatically assisted Electrospray probe or anElectrospray tip in an unassisted ESI ion source probe. Ions producedfrom samples introduced through such sprayers into an API source aresubsequently directed into a desolvation region of the IMS. Autoinjectors may be configured with multiple injector needles configuredfor direct delivery of sample into an API source through one or moreprobes. Such multiple needle auto injectors may deliver samples in asequential or multiplexed manner to such single or multiple directinjection API source ports or probes to maximize sample throughput. Inone embodiment of the invention, a reusable or disposable sampling andspray injection needle may be packed with material, such as C18 coatedbeads, to aid in desalting, sample cleanup or the separation of samplecompounds in solution during the sample pickup, delivery and spraysteps. Different solvent composition layers can be pulled sequentiallyinto such packed sampling and spray needles with attached reservoirsprior to sample pickup. The sample can then be sprayed into an APIsource from such a loaded injection needle using solvent gradients toaid in sample desalting, additional cleanup or sample compoundseparation during spraying.

Washing or flushing of a packed or open disposable injection needle,according to the invention, is not required between injections allowingan increase in sample throughput. In one embodiment of the invention,sample solution may be drawn up into a packed or open disposableinjection needle. The injection needle is subsequently introduced intothe API source and sample solution is sprayed from the injection needletip with or without a solvent gradient to elute sample from any packedmaterial. Alternately, a sample solution can be loaded into anon-disposable or reusable needle and the needle is then inserted intoand forms a seal with a packed disposable injection needle. The packedinjection needle is then introduced into an API source and the samplesolution and any solvent gradient flows from the non-disposable needlethrough the packed disposable needle. The resulting solvent and samplesolution is sprayed from the disposable needle tip into an API source.The packing material in the disposable tip serves to desalt or furtherclean the sample solution as well as to provide some sample componentseparation due to solvent gradient flow, if desired. Depending on therequirements of a specific analytical application, packing material maybe replaced by filter media according to the invention to aid in samplecleanup with a minimum of dead volume.

The invention eliminates the need for sample injector valves or transferlines into an API source, reducing sample dilution, loss andcontamination due to sample handing and transfer. When a reusable needleis configured in the invention, the needle inner bore and outer surfacecan be washed in between each sample delivery and spraying step toreduce or eliminate, chemical noise, cross talk or carry over from onesample to the next. The use of disposable needles, configured accordingto the invention, eliminates sample to sample cross talk orcontamination without a wash step between sample injections into the APIsource. Faster cycle times or more rapid sample injection throughput canbe achieved by eliminating wash steps. Alternatively, a wash step can berun for one or more reusable injection needles while sample delivery andspraying is occurring with another injection needle or needles. Theinvention reduces apparatus costs, sample losses, sample contamination,and sample handling and minimizes solvent consumption and waste whileincreasing sample throughput in flow injection analysis with Atmosphericpressure ion sources. A direct injection needle apparatus may beconfigured with other API inlets in the same API source chamber as ameans to increase analytical flexibility within one API sourceapparatus. Ions produced from the API source may be analyzed by anapparatus other than MS including but not limited to ion mobilityanalyzers.

This invention also describes an apparatus and method for operating theionization source and/or sample inlet at ground or near groundpotential. The configuration will enable the direct electrospray andallow simple interface to API and other sample introduction methods,such as interface a thermal desorber, in this case the thermaldesorption process can happen in the ionization region.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other aspects, embodiments, and features of theinventions can be more fully understood from the following descriptionin conjunction with the accompanying drawings. In the drawings likereference characters generally refer to like features and structuralelements throughout the various figures. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the inventions.

FIG. 1 shows schematic diagram of the prior state of the art IMS system.

FIG. 2 shows schematic diagram of the IMS apparatus of this invention.

FIG. 3 shows the single syringe electrospray for IMS.

FIGS. 4A-B shows an embodiment of the electrospray ionization sourcethat could use a curtain gas section for heat isolation of hightemperature drift gas from the electrospray needle.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

Unless otherwise specified in this document the term “ion mobility basedspectrometer” is intended to mean any device that separates ions basedon their ion mobilities and/or mobility differences under the same ordifferent physical and/or chemical conditions, the spectrometer may alsoinclude detecting the ions after the separation process. Manyembodiments herein use the time of flight type IMS as examples; the termion mobility based spectrometer shall also include many other kinds ofspectrometers, such as differential mobility spectrometer (DMS) andfield asymmetric ion mobility spectrometer (FAIMS). Unless otherwisespecified, the term ion mobility spectrometer or IMS is usedinterchangeable with the term ion mobility based spectrometer definedabove.

As used herein, the term “analytical instrument” generally refers to ionmobility based spectrometer, MS, and any other instruments that have thesame or similar functions. Unless otherwise specified in this documentthe term “mass spectrometer” or MS is intended to mean any device orinstrument that measures the mass to charge ratio of achemical/biological compounds that have been converted to an ion orstores ions with the intention to determine the mass to charge ratio ata later time. Examples of MS include, but are not limited to: an iontrap mass spectrometer (ITMS), a time of flight mass spectrometer(TOFMS), and MS with one or more quadrupole mass filters

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases.

The foregoing and other aspects, embodiments, and features of theinventions can be more fully understood from the following descriptionin conjunction with the accompanying drawings. In the drawings likereference characters generally refer to like features and structuralelements throughout the various figures. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the inventions.

The term ion mobility separator, and ion mobility spectrometer, and ionmobility based spectrometers are used interchangeably in this invention,often referred to as IMS, including time-of-flight (TOF) IMS,differential mobility spectrometers (DMS), field asymmetric ion mobilityspectrometers (FAIMS) and their derived forms. A time of flight ionmobility spectrometer and their derived forms refers to, in its broadestsense, any ion mobility based separation device that characterize ionsbased on their time of flight over a defined distance. A FAIMS, a DMS,and their derived forms separate ions based on their ion mobilitycharacteristics under high values of normalized electric field. The IMSsystems may operate in different drift media, such as gas and/or liquid,in their pure or mixture forms. The operating pressure may vary from lowvacuum to a plurality of atmospheric pressures.

The systems and methods of the present inventions may make use of “drifttubes.” The term “drift tube” is used herein in accordance with theaccepted meaning of that term in the field of ion mobility spectrometry.A drift tube is a structure containing a neutral gas through which ionsare moved under the influence of an electrical field. It is to beunderstood that a “drift tube” does not need to be in the form of a tubeor cylinder. As understood in the art, a “drift tube” is not limited tothe circular or elliptical cross-sections found in a cylinder, but canhave any cross-sectional shape including, but not limited to, square,rectangular, circular, elliptical, semi-circular, triangular, etc. Inmany cases, a drift tube is also referred to the ion transportationand/or ion filter section of a FAIMS or DMS device.

Neutral gas is often referred to as a carrier gas, drift gas, buffergas, etc. and these terms are considered interchangeable herein. The gasis at a pressure such that the mean free path of the ion, or ions, ofinterest is less than the dimensions of the drift tube. That is the gaspressure is chosen for viscous flow. Under conditions of viscous flow ofa gas in a channel, conditions are such that the mean free path is verysmall compared with the transverse dimensions of the channel. At thesepressures the flow characteristics are determined mainly by collisionsbetween the gas molecules, i.e. the viscosity of the gas. The flow maybe laminar or turbulent. It is preferred that the pressure in the drifttube is high enough that ions will travel a negligible distance,relative to the longitudinal length of the drift tube, therefore asteady-state ion mobility is achieved. An IMS can be used at differentpressure conditions.

The apparatus and methods used for flow injection analysis typicallyinclude an injector valve, transfer lines, fluid line connections, anaddition fluid delivery pump, a sprayer probe with internal volume forESI and APCI sources and a switching valve when multiple injector valvesare configured. Each of these elements adds to the dead volume or mixingvolume encountered when delivering a sample solution into an API sourcein flow injection analysis. Added dead or mixing volumes can causesample dilution due to diffusion or mixing of the sample with solventduring sample solution flow into an API source. Sample can adsorb to thewalls of the valve, transfer line and probe transfer tube. Dilution ofsample and loss of sample to the inner surfaces of the flow pathwayresults in reduced ion signal and analytical sensitivity. As liquid flowrates are reduced the sample solution spends more time in the transferdead volumes. Increased transfer time results in increased sampledilution and loss to transfer surfaces. Adsorbed sample can bleed offvalve, transfer line, connector and probe surfaces in subsequentinjections, contributing chemical noise and interference peaks toacquired mass spectrum. Chemical noise or interference peaks due tocontamination from prior injected sample can reduce the accuracy ofquantitative measurements and compromise the limits of detection.Increased valve, connector, transfer line and probe surfaces requireincreased solvent flushing or cleaning time in between sample injectionsto minimize subsequent sample carry over or bleed. This requiredflushing increases solvent consumption and increases the time betweeninjections. Increased cleaning time between injections decreases thenumber of samples that can be injected in a given time period, reducingsample throughput.

The invention allows rapid flow injection analysis over a wide range ofliquid flow rates while minimizing solvent consumption and waste andeliminating all injector valves, fluid line connectors, transfer lines,probe liquid transfer tubes and additional liquid flow delivery systemapparatus. Sample dilution or adsorption losses and solvent consumptionare minimized with the invention and apparatus costs are reduced byelimination of components. Sample carry over or cross talk can beminimized with washing of reusable injection needles or eliminated withdisposable or removable injection needles configured according to theinvention. The invention comprises the configuration and use of aninjector needle to draw up sample solution from a sample vial orcontainer into the injector needle and attached solvent reservoir,transfer of the sample solution to an API source probe, passing of theinjector needle through the API source probe channel and spraying of thesample solution from the tip of the injector needle into an API source.Ions are produced from the sprayed solution in the API source and aredirected into the IMS where they are analyzed. API sources may includebut are not limited to ESI, APCI or Inductively Coupled Plasma (OCP) ionsources.

Commercially available auto-injectors such as the Leap HTS PAL systemare configured with syringes for the uptake, movement and injection ofsamples into injector valves. The syringes and attached injector needlesare typically mounted to a programmable x-y-z position translator arm.Under pre-programmed control, sample solution is removed from a selectedsample vial or vials, the loaded injector needle is moved to a positiondirectly in-line with the bore of an ESI probe assembly and the injectorneedle is introduced through the bore of the ESI probe assembly in anESI source. Some commercially available auto-injectors are configuredwith multiple syringes. FIA sample throughput can be increased accordingto the invention when such multiple syringe auto-injectors are used.Such a multiple syringe auto-injector configuration can be operatedwhereby one syringe is spraying sample solution into ES source while asecond syringe is being flushed and cleaned prior to loading the nextsample solution to be sprayed into the second injector needle andsyringe. The syringes can be partially or completely filled with samplesolution for each FIA run. The fill and spray liquid flow rates aredetermined by the syringe size used and the plunger movement rate asprogrammed in the auto-injector. Commercially available auto-injectorsare configured to flush the internal bore of the syringe and injectionneedle and wash the injection needle external surface.

In one alternative embodiment, samples can be prepared using the samesyringe and direct sprayed into the IMS device for analysis. The IMSdevice could be used to analyze complex samples using simple step samplepreparation methods on the fly. These methods may include, but are notlimited to, solid phase microextraction (SPME) and microextraction bypacked sorbent (MEPS). A SPME fiber can be used to extract andpreconcentrate gaseous or aqueous analytes; the analytes will then bedesorbed into electrospray solvent for direct injection into the IMS foranalysis. Alternatively, volatile and semi-volatile analytes could bethermally desorbed into the device and ionized in the desolvation regionvia SESI or other API methods. MEPS is a extraction technique thatallows rapid sample preparation using in-syringe solid phase extraction.The syringe would then be directly inserted into the IMS for analysis. Avariety of sorbents are commercially available.

For prior art IMS systems, the Faraday detectors are operated at groundor near-ground potential, and thus the other end of the drift tube, theion source end, is set at high voltage. For positive ion detection, apositive voltage is applied at the ion source end; similarly fornegative ion detection, a negative voltage is applied. State of artportable IMS systems have been generally developed for gas monitoringonly, since the gas-phase sample can be guided into the ionizationsource via a non-conductive flow path. For an ESI source, the liquidsample needs to be delivered to the electrospray needle, and the liquidsample is generally conductive. This fact makes the handheld ESI-IMSchallenging, since sample handling and injection pose a safety hazard.Developing a floating pre-amplifier that could be operated at highvoltage allows the current invention to set the ionization source atground and the Faraday detector at a high potential of the oppositepolarity, i.e. positive potential for negative ions and negativepotential for positive ions.

FIG. 1 shows the prior art IMS systems, the ionization source 100 isoperated at the highest potential 101 of the drift tube and the Faradayion detector 102 is operated at the lowest potential, substantially atground potential 103. In various embodiments, a time of flight type ofion mobility spectrometer uses a ionization source 100, sample inlet, incase electrospray ionization source, the sample inlet is also theionization source 100, desolvation/ionization (reaction) region 104, iongate 105, drift region 107, aperture grid, ion detector 102, andpre-amplifier 109 that are organized on a continuous potential gradientconnected with a resister chain. In case of prior art IMS, theionization source or sample inlet are at high potential and ion detectoris at low potential of this gradient. The current invention describesusing an ion detector 202 (typically a Faraday plate) and apre-amplifier 209 that operates at a high voltage 201, such as highvoltage (potential) can either be positive or negative potential asshown in FIG. 2, in a range of 200-40000 V, in particular 1000V, 5000 V,10,000 V with similar gain and rise time as the state-of-the-artamplifiers operating at near ground potential (such as the Keithley428-PROG Programmable Current Amplifier, Cleveland, Ohio). In thisnon-limiting example, FIG. 2 shows a desolvation/ionization (reaction)region 204, ion gate 205, drift region 207, and a sample inlet port 215.This invention allows the ionization source 200, e.g. ESI or APCIsource, and components that may need to be accessible during theanalysis procedure to be set at substantially low voltage, such as, atground potential 203. It will isolate users from high voltage componentsso that they can directly handle and inject samples into the IMS.

Basic operation of the IMS system will involve obtaining a sample anddirectly introducing the sample into the IMS device via direct syringespray or other API source. The main advantages of the syringe directspray include: 1) rapid testing, since a sample could be analyzed withinone minute; 2) no cross contamination, since there is no carry-over fromprevious samples as the sample is directly delivered from the syringe tothe desolvation region of the detector. Flow rates for common ESImethods are typically at about 1-10, 10-100, and can be substantiallyincrease to 100-1000, 1000-5000 μL/min, etc., and each test may becompleted in a time-span ranging from several milliseconds seconds aminute, depending on the amount of signal averaging required. This meansthat very little solvent is required. If the analyte is sufficientlyconcentrated such that direct measurement is possible, an aqueous samplemay be directly diluted with organic solvents, such as methanol, forstable electrospray. The sample preparation method may involve: a 10 μLsyringe may be preloaded with 1 μL methanol; subsequently 1 μL ofaqueous sample would be drawn up, and the syringe would then be insertedinto the ESI source for direct measurement. A thermal desorber/secondaryelectrospray ionization (SESI) source module could also be used, whichwould allow analysis of gas phase and solid phase samples. SESI involvesspraying electrospray solvent to deliver charged solvent droplets intothe desolvation region; the charged solvent droplets are then used toionize gas-phase samples.

In one embodiment, the direct syringe spray method uses a single syringethat has a needle in the diameter that could be used to directly spraysample into the spectrometer. For this purpose, there is an electricalcontact that is attached to the syringe needle, but no other assemblycomponent is needed for this ionization source. The syringe is used todraw samples from a liquid reservoir (sampling) and then spraying thesample into the spectrometer using the same or a replacement needle. Thesingle syringe needle spray ionization source can be used with an priorart ion mobility based spectrometer or the ion mobility basedspectrometer that the ionization source is at ground or near groundpotential.

The IMS system with the ionization source at near ground potential willnot only benefit the direct analysis of liquid samples, but also alloweasier sample introduction of gas and solid sample. With a thermaldesorber, it can also be used to analyze gas phase and solid phasesamples (first evaporated with the thermal desorber) and then ionizeusing SESI or other API methods. The combined thermal desorber/SESIsubsystem will allow the user to switch between a direct liquidinjection mode and a thermal desorption/gas sampling mode in-situ. Thegas-phase sample, either directly from the surrounding environment orfrom thermal desorption of the solid-phase sample, is pulled into thedesolvation region via the gas inlet and ionized by the chargeddroplets.

In various embodiments, the ground potential can also be located in themiddle of a drift tube, such as the sample inlet before the ion gate. Inthis case, for positive ion measurement, the ionization source ispositive potential, the sample inlet port location is at ground, and theFaraday detector is at negative potential; the potential gradient willbe reversed for negative ion measurement. Setting the sample port atground potential allow users directly insert sample into the samplingport without safety concerns.

In one embodiment of direct syringe spray ion mobility spectrometer, asshown in FIG. 3 the liquid sample in syringe 301 is directlyelectrosprayed into the desolvation/reaction region 302 of the ionmobility spectrometer (where the curtain gas section is not shown). Inaddition, a gas sample inlet port could be added to the desolvationregion where the gas phase sample could be ionized undergoing secondaryelectrospray ionization. In case the syringe needle 301 is replace byother ionization sources operated at ground or near ground potential,the ionization process of the gas phase sample will undergo othersecondary ionization processes. Ions formed in the desolvation region orreaction region are analyzed by ion mobility analyzer 304 in the driftgas that is preheated or mixed to designated temperature and/or otherconditions using the gas preheating/mixer subsystem 305.

In one embodiment of the ESI-IMS system, the electrospray ionizationsource comprises an electrospray needle, curtain (cooling) gas sectionand desolvation region and other components of IMS. The ionizationsource is operated at substantially at atmosphere pressure. The curtainsection is placed between desolvation region and electrospray needle(the ionization source), the curtain section is to substantiallythermally isolate the electrosprayer needle from heated gas ofdesolvation region (desolvation gas).

The electrospray ionization source consists of an electrospray needle,curtain gas section and desolvation region. The ionize source isoperated at substantially at atmosphere pressure. The lowered gastemperature at electrospray needle region will provide a favorableenvironment for electrospraying by avoiding boiling of the analytesolution in the electrospray needle and at the tip of electrosprayneedle, by high temperature gas. It is beneficial to have this curtaingas section to separate the electrospray needle from the hightemperature desolvation, especially when a syringe needle is used as theelectrospray needle without other additional components surround thebare needle tip. The electrospray needle is at a high electricalpotential relative to the adjacent electrodes to generate chargeddroplets. The charged droplets generated from the electrospray needlewill be transported to the desolvation region through the curtain gassection and desolvated at desolvation region and ions will be generated.The ions in the desolvation region will be gated to the drift region forion mobility analysis. The ions in the desolvation region can be furthertransported to high vacuum to be analyzed by mass spectrometer. Thecurtain gas section provides positive or negative gas flow. For positivecooling gas flow, the cooling gas will be at lower temperature than thegas at the desolvation region, and will lower the gas temperature at theelectrospray needle region. For negative cooling gas flow, the coolinggas flow will lower the gas temperature at the electrospray needleregion than the gas temperature without negative cooling gas flow.

One embodiment of the invention is an ion mobility based spectrometerapparatus comprising: an ionization source that is connect to a firstend drift tube and an detector that is connected to the second end ofthe drift tube; a high potential is applied to operate the spectrometer;at least one section of the ionization source is set at ground orsubstantially near ground potential; and at least one section of thedetector and/or the preamplifier is set at the high potential byconnecting to an high voltage power supply. The end of the ionizationsource is set at near ground potential that is a voltage that issubstantial safe to touch. The high potential can be either positive ornegative high potential. The ion mobility based spectrometer has asample introduction port. The ground or near ground potential can be setat the sample introduction port. The sample introduction port may locateinside the ionization source or substantially downstream from theionization source toward the ion detector.

In various embodiments, an ion mobility based spectrometer (FIG. 4A and4B is shown as an example) does not necessary use an electrosprayionization source. FIG. 4A and 4B shows a desolvation/ionization(reaction) region 403, ion gate 410, drift region 401, electrosprayneedle 405, drift gas flow 412, (optional) aperture grid 414 and adetector 415. FIG. 4A shows a non-limiting example of a curtain gas 407at negative flow and FIG. 4B has a curtain gas 407 at positive flow. Thecurtain gas section could be used as a universal interface to bringcharged particles or ions into the ion mobility based spectrometer. Allionization sources that are suitable the ion mobility basedspectrometers could be used. Such sources could be, but not limited to,secondary electrospray ionization, DART ionization, DESI, MALDI, APCI,corona discharge, radioactive ionization.

One embodiment of the ion mobility based spectrometer apparatus has theionization source set at a low potential for the spectrometer and theion detector is set at a high potential whereby the ionization source onone end and the ion detector on the other end are in fluidcommunication. The low potential is the lowest potential for thespectrometer at ground or near ground potential whereby the highpotential is the highest potential for the spectrometer. The highpotential can be either positive or negative potential. The ion mobilitybased spectrometer can optionally have sample inlet which can be set atthe lowest potential. The ionization source can be various, such aselectrospray, DART, corona discharge, electron beam, radioactive ⁶³Ni,but not limited to only these examples. When using electrosprayionization, a fixed needle can be used as well as a needle that is usedfor sampling and as the spray needle. Therefore, the ion mobility basedspectrometer can be operated where an ionization source on one end is influid communication with an ion detector on the other end; setting theionization source at a low potential of the spectrometer; and settingthe ion detector at a high potential of the spectrometer. The lowpotential is set at the lowest potential for the spectrometer at groundor near ground potential. The high potential is set at the highestpotential for the spectrometer and can be set at either positive ornegative potential. The spectrometer can be operated using a sampleinlet as well whereby the sample inlet is set at the lowest potential.The sample can be electrosprayed from a needle which can be used forsampling and spraying.

Another embodiment of the ion mobility based spectrometer apparatus hasa curtain gas section which has at least two plates with an opening inthe center. The plates are positioned to administrator gas flow as such:a low temperature cooling gas flow enters the center hole of the firstplate on the needle side; a high temperature desolvation gas flow entersthe center hole of the second plate on the desolvation section side;both gas flows are exhausted at a gas exit located between the twoplates. The plates can be set at different potentials that guide ionsentering the first plate toward the second plate. The gas exit could beused as a gas inlet for the cooling gas flow and exhaust both coolinggas flow and the desolvation gas flow from the center hole of the firstplate. Therefore, the ion mobility based spectrometer administers acurtain gas wherein the curtain gas flow is administered as such: a lowtemperature cooling gas flow enters a center hole of a first plate onthe needle side; a high temperature desolvation gas flow enters thecenter hole of a second plate on the desolvation section side; both gasflows are exhausted at a gas exit. The plates can be set at differentpotentials that guide ions entering the first plate toward the secondplate. The cooling gas flow can be used as a gas inlet and exhaustwhereby both the cooling gas flow and the desolvation gas flow from thecenter hole of the first plate.

It is recognized that modifications and variations of the inventiondisclosed herein will occur to those of ordinary skill in the art and itis intended that all such modifications and variations be includedwithin the scope of the appended claims. The contents of all of thepatents and literature articles cited herein are incorporated into thisspecification by reference.

1. An ion mobility based spectrometer apparatus comprising: a) anionization source that is set at a low potential of the spectrometer; b)an ion detector that is set at a high potential of the spectrometer; andc) an ion mobility based analyzer that is in fluid communication withthe ionization source on one end and the ion detector on the other end.2. The ion mobility based spectrometer apparatus of claim 1, wherein thelow potential is the lowest potential for the spectrometer at ground ornear ground potential.
 3. The ion mobility based spectrometer apparatusof claim 1, wherein the high potential is the highest potential for thespectrometer.
 4. The ion mobility based spectrometer apparatus of claim1, wherein the high potential is either positive or negative potential.5. The ion mobility based spectrometer apparatus of claim 1, furthercomprises a sample inlet.
 6. The ion mobility based spectrometerapparatus claim 5, wherein the sample inlet is set at the lowestpotential.
 7. The ion mobility based spectrometer apparatus of claim 1,wherein the ionization source is an electrospray ionization source. 8.The ion mobility based spectrometer apparatus of claim 7, wherein theelectrospray ionization source comprises a syringe needle that is usedfor sampling and as the spray needle.
 9. The ion mobility basedspectrometer apparatus of claim 7, further comprises a curtain gassection which has at least two plates with an opening in the center. 10.The ion mobility based spectrometer apparatus of claim 9, wherein theplates are positioned to administrator gas flow as such: a lowtemperature cooling gas flow enters the center hole of the first plateon the needle side; a high temperature desolvation gas flow enters thecenter hole of the second plate on the desolvation section side; bothgas flows are exhausted at a gas exit located between the two plates.11. The ion mobility based spectrometer apparatus of claim 9, whereinthe plates are set at different potentials that guide ions entering thefirst plate toward the second plate.
 12. The ion mobility basedspectrometer apparatus of claim 10, wherein the gas exit could be usedas a gas inlet for the cooling gas flow and exhaust both cooling gasflow and the desolvation gas flow from the center hole of the firstplate.
 13. An ion mobility based spectrometer method comprises:operating an ion mobility based analyzer that is in fluid communicationwith an ionization source on one end and an ion detector on the otherend; setting the ionization source at a low potential of thespectrometer; and setting the ion detector at a high potential of thespectrometer.
 14. The ion mobility based spectrometer method of claim13, wherein the low potential is set at the lowest potential for thespectrometer at ground or near ground potential.
 15. The ion mobilitybased spectrometer method of claim 13, wherein the high potential is setat the highest potential for the spectrometer.
 16. The ion mobilitybased spectrometer method of claim 13, wherein the high potential is setat either positive or negative potential.
 17. The ion mobility basedspectrometer method of claim 13, further comprises setting a sampleinlet at the lowest potential.
 18. The ion mobility based spectrometermethod of claim 13, further comprises electrospraying a sample from asyringe needle.
 19. The ion mobility based spectrometer method of claim18, further comprises using the needle for sampling and spraying. 20.The ion mobility based spectrometer method of claim 13, furthercomprises administering gas flows in the curtain gas section as such: alow temperature cooling gas flow enters a center hole of a first plateon the needle side; a high temperature desolvation gas flow enters thecenter hole of a second plate on the desolvation section side; both gasflows are exhausted at a gas exit between the first and second plate.